seems everyone has given you good info but figured id through in my 2 cents since ive grown jack herer twice and didnt make the same mistakes i did the first time...

the first time i grew this i topped them when they were about 10 inches and let veg for another week and then turned to flower.... they grew massive even tho i thought they were topped quite soon either way the stretch was like 4x and they still continued to grow taller up to harvest.

this time around i wanted more bud sites but didnt want them to get as tall i topped them around 15 inches with about 7-10 nodes then i moved them to flower about 3 days later. once they got about 2 1/2 feet and realized at this rate i was gonna run outta space i tied them over 90 degrees about the 2nd or third node down. seems to work great they only stretched about another 10 inches and get more light to the good spots. anyway i have large bushes now and they are only about 3 -3 3/4 feet from top of soil and looking great

hopes this helps at all

ps remember jack herer is a conosuir plant not a commercial one it has nice yields but can take up to 11 weeks to finish flowering ive read fem JH will finish sooner which is what i had they were 90% ready for harvest at 9 weeks